2001 Nissan Maxima problems?

I have a 2001 Nissan Maxima that I bought recently for $6,000 with about 65,000 miles on it. When we first bought it it was running fine with no problems. But recently, the service engine soon light has been coming on, this is the third time it has come on in the past couple of months. The car also sputters when I brake, and there is a foul odor that smells like rotten eggs sometimes. It sputters off and on, sometimes it wont sputter at all all day. We have taken it to a repair shop twice, and have paid $500 for repairs, but it has done nothing. It still has all the same problems. Does anyone know what this is? Is this a normal problem with Maximas, should I just get rid of the car?